Lapping machine fixture



Oct. 27, 1970 J. v. KEI-:FE ET AL y LAPPING MACHINE FIXTURE Filed Jan. 22. 1968 n/72 f6.2 6,4 r/// ///1/ JQ Wap/5 yheefa,

n b 1f 61957104 /Qlfi Jose W5 md# United States Patent O U.S. Cl. 51-217 10 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention The present invention relates generally to lapping machines, and more particularly to a fixture for use therewith in lapping an exterior annular radial shoulder of a workpiece.

Description of the prior art One type of lapping machinel adapted for shoulder lapping includes a lapping disc having an upwardly facing annular channel and presenting a horizontal lapping surface comprised of inner and outer annular zones. A ringlike workpiece may be disposed to extend axially into the annular channel with the intermediate exterior annular radial shoulder thereof positioned for lapping on the lapping surface. As the lapping disc is rotated, the workpiece is permitted to rotate on its own axis while being held against rotation about the axis of the lapping disc. This shoulder lapping arrangement has not proved to be entirely satisfactory. Because of the small area, of essentially two-point contact between the shoulder and the lapping surface at the opposite sides of the annular channel, the workpiece during lapping is unstable. As a consequence, diiiiculty has been experienced in obtaining a truly at shoulder and a shoulder that is parallel to the top of the workpiece.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a fixture which supports the workpiece from above. More specifically, the fixture comprises a ring portion having a bottom surface engaging the lapping surface, and means for mounting the workpiece in the fixture with the shoulder of the -workpiece positioned on the lapping surface. The ring portion overlaps the inner and outer peripheries of the inner and outer annular lapping zones respectively. In this manner, the ring portion provides a four-point support for the workpiece on the lapping surface and increases the supporting contact area with the lapping surface whereby the workpiece is stabilized during lapping and only the high spots on the shoulder are lapped. The ring portion also serves to dress the lapping surface and eliminates the need for a separate conventional truing ring. In addition, the workpiece is adjustably mounted in the fixture whereby the shoulder of the workpiece may be positioned in the plane of the bottoni of the ring portion for parallel and flat lapping. Other features and advantages of the present invention will become apparent from the following detail description.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a plan view of a lapping machine with which are associated fixtures of the present invention;

3,535,830 Patented Oct. Z7, 1970 FIG. 2 is a vertical sectional view on an enlarged scale, taken substantially along the line 2-2 in FIG. l, looking in the direction indicated by the arrows; and

FIG. 3 is a sectional View, on a further enlarged scale, of one of the fixtures, and a portion of the lapping disc, Of FIG. 2.

DESCRIPTION O'F THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2, there is indicatedgenerally by the reference numeral 10 a bench-type lapping machine with which fixtures of the present invention may be used. The lapping machine 10 includes a generally rectangular housing 12 in the top wall of which is provided a circular opening 14 for receiving a horizontal lapping wheel or disc 16.

The lapping disc 16 is secured to a driving hub 18 which is journalled in a tubular support 20 suspended from a combined drip pan and supporting member 22 depending from the top wall of the housing 12. The driving hub 18 is keyed to the drive shaft 24 of a worm-drive gear box 26 which, together with an operatively connected drive motor 28, is carried by the tubular support 20. The abovedescribed drive means serves to support the lapping disc 16 and to drive the same in a counterclockwise direction as viewed in FIG. 1.

Mounted at one side of the lapping disc 16 is an inclined cylindrical container 30 having a helically wound tube 32 lixedly mounted therein. The container 30 is adapted to be rotated by a gear box 34 and an electric motor 36. A liquid carrier, such as light oil, with abrasive particles in suspension is placed in the container 30, and the abrasive mixture is fed therefrom through the tube 32 to the lapping disc 16 upon rotation of the container. Used abrasive mixture iiowing from the lapping disc 16 is collected in the drip-pan supporting member 22 and is drained therefrom through a drain spout 38. A wiper bar 40 is threaded into the driving hub 18 for rotation therewith, and the free end thereof serves to sweep collected abrasive material toward the drain spout 38.

For further details concerning the construction and operation of the lapping machine 10, reference may be had to U.S. Letters Pat. Nos. 3,110,991 and 3,110,992.

For use in shoulder lapping, the lapping disc 16 is formed with an upwardly facing annular channel 42, and presents a horizontal lapping surface comprised of an inner annular zone 44 and an outer annular zone 46. One class of workpieces which requires shoulder lapping are indicated at 48 in FIGS. 2 and 3. Each ring-line workpiece 48 has a top surface 50, a bottom surface 52, and an intermediate exterior annular radial shoulder 54. The workpiece 48 is adapted to be disposed to extend axially into the annular channel 42 with the radial shoulder 54 positioned for lapping on the lapping surface of disc 16.

Associated with each of the lworkpieces 48 is a lapping iixture 56 which is comprised of a stabili-zing ring portion or member 58 havinga bottom surface 60, and means for mounting the workpiece in the lfixture. More specifically, the lapping fixture 56 includes a body portion in the form of a first horizontal plate 62 secured to the ring member 58 across the top thereof, a second horizontal plate 64 parallel to the first plate 62 and adjustably distanced therebelow within the confines of the ring 58, and a third horizontal plate 66 parallel to the second plate 64 and spaced therebelow. A bolt 618 is disposed through the third plate 66 and threaded into the second plate 64 for fastening these plates together with the workpiece 48 therebetween. Preferably, a pad member 69 of felt or the like is interposed between the third plate 66 and the bottom surface 52 of the workpiece. In addition, set screws 70 are provided in the first plate 62 for engaging the second plate 64 to adjust the distance therebetween whereby the shoulder 54 of the workpiece 48 may be positioned in the plane of the bottom surface 60 of the stabilizing ring 5S, and bolts 72 are inserted through the first plate 62 and threaded into the second plate 64 for fastening these plates together in adjusted position.

After the workpiece 48 has been mounted and properly adjusted within the fixture 56 as shown in solid lines in FIG. 3, the assembled unit is lowered to the position shown in dotted lines. In relation to the size of the lapping disc 16 and workpieces 48 illustrated, four work pieces may be lapped simultaneously by the machine 10. The fixtures 56 are maintained in circumferentially spaced relation by means of a central horizontal roller spacer '74 carried by the drive shaft 24 and roller stops 76 mounted on the housing 12 slightly offset forwardly from the radial line of the disc and fixture centers as shown in FIG. 1. When the disc 16 is rotating, the fixtures 56 are free to rotate on their own axes due to frictional contact of the rings 58 with the disc 16, but are prevented from rotating about the axis of the disc 16 by the roller stops 76.

During rotation of the lapping disc 16, a suitable abrasive mixture is fed thereto from the container 30, and the shoulder 54 of each workpiece 48 is lapped to the extent required. As will be appreciated, because the workpiece 48 is supported from above by the fixture 56, only the high spots on the shoulder are lapped. Moreover, the ring member -58 is fabricated of a material having substantially the same abrasion resistance as the material of the workpiece; therefore, the ring member wears at the same rate as the workpiece shoulder is lapped. Also, the ring member 58 overlaps the inner periphery of the inner annular lapping zone 44 and the outer periphery of the outer annular lapping zone 46, thus providing a four-point support for the workpiece on the lapping surface and increasing the supporting contact area with the lappingsurface. With the foregoing arrangement, the workpiece is stabilized during lapping, and the shoulder is lapped fiat and parallel to the top surface 50 of the workpiece. In addition, the ring member 58 serves to dress the lapping surface and eliminates the need for a separate conventional truing ring.

While there has been shown and described a preferred embodiment of the present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. For use in stabilizing a workpiece having an exterior annular radial shoulder positioned for lapping on the horizontal lapping surface of a rotating lapping disc, a fixture comprising a ring portion having a bottom surface engaging the lapping surface, and mounting means for adjustably securing the workpiece in said fixture with the shoulder of the workpiece positioned in the plane of the bottom surface of said ring portion.

2. For use with a lapping machine including a horizontal lapping disc having an upwardly facing annular channel and presenting a horizontal lapping surface, a fixture for stabilizing a workpiece which extends axially into the annular channel and which has an intermediate exterior annular radial shoulder positioned for lapping on the lapping surface, said fixture comprising a ring portion having a bottom surface engaging the lapping surface, a body portion carried by said ring portion, and mounting means for adjustably securing the workpiece to said body portion with the shouder of the workpiece positioned in the plane of the bottom surface of said ring portion.

3. The fixture of claim 2 wherein said body portion is comprised of a first horizontal plate secured to said ring portion across the top thereof.

`4. The fixture of claim 3 wherein said mounting means is comprised of a second horizontal plate parallel to said first plate and adjustably distanced therebelow within the confines of said ring portion, and means for securing the work piece to the underside of said second plate.

5. The fixture of claim 4 characterized by the provision of set screws in one of said plates for engaging the other of said plates to adjust the distance therebetween, and means for fastening said first and second plates together in adjusted position.

6. The fixture of claim 4` wherein said securing means is comprised of a third horizontal plate parallel to said second plate and spaced therebelow, and means for fastening said second and third plates together with the workpiece therebetween.

7. The fixture of Claim 6 characterized by the provision of set screws in said first plate for engaging said second plate to adjust the distance therebetween, and means for fastening said first and second plates together in adjusted position.

8. The fixture of claim 7 including a pad member interposed between said third plate and the workpiece.

9. The fixture of claim 8 wherein said ring portion is fabricated of a material having substantially the same abrasion resistance as the material of the workpiece.

10. A lapping fixture for a workpiece having a top surface and a bottom surface and an intermediate exterior annular radial shoulder parallel to the top surface, comprising a ring member, a first horizontal plate secured to said ring member across the top thereof, a second horizontal plate parallel to said first plate and spaced therebelow within the confines of said ring member, a third horizontal plate parallel to said second plate and spaced therebelow, means for fastening said second and third plates together with the workpiece therebetween, set screws in said first plate for engaging said second plate to adjust the distance therebetween whereby the shoulder of the iworkpiece may be positioned in the plane of the bottom of said ring member, and means for fastening said first and second plates together in adjusted position.

References Cited UNITED STATES PATENTS 1,235,957 `8/1917 Bidwell.

2,597,382 5/1952 Roshong 51-131 2,612,821 10/1952 Skay.

2,653,423 9/1953 White 51--131 2,788,620 4/1957 Marcus 51-131 2,826,009 3/1958 Shurson 51-131 X 3,166,875 1/ 1965 Litman.

3,284,960 11/1966 Day 51-131 X HAROLD D. WHITEHEAD, Primary Examiner U.S. Cl. X.R. 51-131, 236 

